Inline entity text should not expand when adding text at the end of the entity

[thibaudcolas]

At the moment, text entered after an entity is automatically added to it. This is quite annoying when dropping a link in the middle of a sentence, and is not the behavior of other editors. Instead, the entity text should stop at the last character the entity was added on (and expand only if text is added between the first and last characters).

[thibaudcolas]

@vincentaudebert if you can have a look into this that's probably the most problematic out of all the issues on the backlog. I have no idea how to troubleshoot this though.

[thibaudcolas]

This is facebookarchive/draft-js#430. Trying to use one of the workarounds from that thread.